Isoprenoids constitute an extremely large and diverse group of natural products that have a common biosynthetic origin, i.e., a single metabolic precursor, isopentenyl diphosphate (IPP). Isoprenoid compounds are also referred to as “terpenes” or “terpenoids.” Over 40,000 isoprenoids have been described. By definition, isoprenoids are made up of so-called isoprene (C5) units. The number of C-atoms present in the isoprenoids is typically divisible by five (C5, C10, C15, C20, C25, C30 and C40), although irregular isoprenoids and polyterpenes have been reported. Important members of the isoprenoids include the carotenoids, sesquiterpenoids, diterpenoids, and hemiterpenes. Carotenoids include, e.g., lycopene, β-carotene, and the like, many of which function as antioxidants. Sesquiterpenoids include, e.g., artemisinin, a compound having anti-malarial activity. Diterpenoids include, e.g., taxol, a cancer chemotherapeutic agent.
Isoprenoids comprise the most numerous and structurally diverse family of natural products. In this family, terpenoids isolated from plants and other natural sources are used as commercial flavor and fragrance compounds as well as antimalarial and anticancer drugs. A majority of the terpenoid compounds in use today are natural products or their derivatives. The source organisms (e.g., trees, marine invertebrates) of many of these natural products are neither amenable to the large-scale cultivation necessary to produce commercially viable quantities nor to genetic manipulation for increased production or derivatization of these compounds. Therefore, the natural products must be produced semi-synthetically from analogs or synthetically using conventional chemical syntheses. Furthermore, many natural products have complex structures, and, as a result, are currently uneconomical or impossible to synthesize. Such natural products must be either extracted from their native sources, such as trees, sponges, corals and marine microbes; or produced synthetically or semi-synthetically from more abundant precursors. Extraction of a natural product from a native source is limited by the availability of the native source; and synthetic or semi-synthetic production of natural products can suffer from low yield and/or high cost. Such production problems and limited availability of the natural source can restrict the commercial and clinical development of such products.
The biosynthesis of isoprenoid natural products in engineered host cells could tap the unrealized commercial and therapeutic potential of these natural resources and yield less expensive and more widely available fine chemicals and pharmaceuticals. A major obstacle to high level terpenoid biosynthesis is the production of terpene precursors. In Saccharomyces cerevisiae, the mevalonate pathway provides for production of isopentenyl diphosphate (IPP), which can be isomerized and polymerized into isoprenoids and terpenes of commercial value. Other valuable precursors are also produced, including farnesyl diphosphate (FPP) and geranylgeranyl diphosphate (GPP). However, much of the reaction flux is directed towards the undesired later steps of the sterol pathway, resulting in the production of ergosterol.
There is a need in the art for improved isoprenoid-producing or isoprenoid precursor-producing host cells that provide for high-level production of isoprenoid compounds, as well as the polyprenyl diphosphate precursors of such compounds. The present invention addresses this need and provides related advantages.
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